Curiosity is headed toward the dark Bagnold Dunes, which lie in the northwestern foothills of the towering Mount Sharp, and should begin investigating the sandy feature in the next few days, NASA officials said.

The Bagnold Dunes are substantial; Curiosity will study one dune that's as wide as a football field and as tall as a two-story building, NASA officials said. And they're active; observations by Mars orbiters show that some of the dunes are moving by as much as 3 feet (1 meter) per year. [?Amazing Mars Rover Curiosity's Latest Photos]

"We've planned investigations that will not only tell us about modern dune activity on Mars but will also help us interpret the composition of sandstone layers made from dunes that turned into rock long ago," Bethany Ehlmann of the California Institute of Technology and NASA's Jet Propulsion Laboratory, both of which are located in Pasadena, California, said in a statement.

While Mars rovers have visited sandy swales in the past, no active dunes (which feature slopes steep enough for sand to slide down) have ever been studied up close on a world beyond Earth, NASA officials said.

When Curiosity reaches the Bagnold Dunes - which the mission team informally named after British military engineer, explorer and dune researcher Ralph Bagnold (1896-1990) - the rover will collect samples for analysis by its onboard instrument suite and scrape at the sand with a wheel to investigate differences between the surface and subsurface.

"These dunes have a different texture from dunes on Earth," Nathan Bridges, of the Johns Hopkins University's Applied Physics Laboratory in Laurel, Maryland, said in the same statement.

"The ripples on them are much larger than ripples on top of dunes on Earth, and we don't know why," added Bridges, who leads the planning for Curiosity's dune work along with Ehlmann. "We have models based on the lower air pressure. It takes a higher wind speed to get a particle moving. But now we'll have the first opportunity to make detailed observations."

The 1-ton Curiosity rover touched down inside Mars' huge Gale Crater in August 2012, on a $2.5 billion mission to determine if the Red Planet could ever have supported microbial life. The robot quickly answered that question in the affirmative, finding that Gale harbored a habitable lake-and-stream system in the ancient past.

The 3.4-mile-high (5.5 kilometers) Mount Sharp rises from the center of Gale Crater. Curiosity reached the mountain's base in September 2014 after a 14-month drive, and the rover is now working its way slowly up the mountain, reading a history of Mars' changing environmental conditions in the rocks as it goes.

Mars plays host to a huge number of dune fields -- regions where fine wind-blown material gets deposited to form arguably some of the most beautiful dunes that can be found on any planetary body in the solar system. Using the powerful High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter, planetary scientists have an orbital view on these features that aid our understanding of

" -- elliptical accumulations of fine material with no-slip surfaces. These domes contrast greatly with the often jagged appearance of barchan dunes. Found at the bottom of Proctor Crater, they are darker than the surrounding crater floor as they are composed of dark basaltic sand that was transported by the wind.

Looking like a wind-blown silk sheet, this field of "star dunes" overlays a plain of small ripples, another aeolian feature. The ripples move more slowly across the bottom of Proctor Crater, so the large dune field will travel

over

the smaller ripples. Dunes are continuously evolving and moving with the wind, ensuring that the Martian surface is never static.

Resembling the mouths of a shoal of feeding fish, this is a group of barchan dunes in Mars' North Polar region. Barchan dunes betray the prevailing wind direction. In this case, the prevailing wind is traveling from bottom right to top left; the steep slope of material (plus dune "horns") point to the downwind direction. The HiRISE camera monitors barchans to see if they move between observing opportunities, thereby revealing their speed of motion across the Martian plains.

...only when zoomed out does the true nature of this fascinating region become clear. The prevailing wind is eroding the mesas (small hills) to the right of the image, carrying fine material downwind (from right to left), creating a startling pattern of barchans and a viscous-looking trail of sandy ridges across the plains.

The band Train sang about the "Drops of Jupiter" -- what about the "Drops of Mars"? Sure, they're not made of any kind of fluid, but they do make for incredibly-shaped dunes. These raindrop-shaped dunes are found in Copernicus Crater and are known to be rich in the mineral olivine, a mineral that formed during the wet history of Mars' evolution.